Dynamics of Biofilm Regrowth in Drinking Water Distribution Systems

Abstract

The majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment, yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics, with findings demonstrating patterns of material accumulation, seasonality, and influential factors. Rigorous flushing operations repeated over a 1-year period on an operational chlorinated system in the United Kingdom are presented here. Intensive monitoring and sampling were undertaken, including time-series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. The results show that bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals, and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to residual chlorine, this suggests that limiting inorganic nutrients, rather than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, giving another reason for flushing being a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimize asset performance.IMPORTANCE This research provides novel information regarding the dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimize the performance of the distribution network and to guarantee safe and good-quality drinking water to consumers.

Decision-Making Tools to Manage the Microbiology of Drinking Water Distribution Systems

“…Biofilms can be defined as a dynamic sessile community of cells attached, in this case, to the walls of the pipes, and embedded in a matrix of extracellular polymeric substances that they have produced [11]. Biofilm accumulation on pipe surfaces can be influenced by different DWDS properties, like pipe characteristics including composition, diameter, roughness, etc., hydrodynamic conditions or nutrient availability like phosphate [12]. Also, they can alter the quality of water, participating in metal bio-corrosion processes [13], discolouration events [14] and act as reservoirs for opportunistic pathogens [15,16].…”

“…The survival and regrowth of microorganisms in DWDS will be affected not only by microbiological factors, but also the interaction with various physicochemical factors [12,23]. In this regard, a study aimed at bounding the main parameters of water networks and the presence of particular bacteria would be valuable to understand how these two aspects influence each other and could result in the implementation of an effective risk management plan [24].…”

“…The present application is carried out by using the input data published by Douterelo et al [12], by taking into account the measurements of elements (water quality parameters and bacteria relative abundance), from flushing trials repeated four times in one year, of plastic and cast iron pipes.…”

Effect of chlorination and pressure flushing of drippers fed by reclaimed wastewater on biofouling

“…Pseudomonas and Pseudoxanthomonas genera (γ-Proteobacteria). β-Proteobacteria are frequently found in chlorinated drinking distribution systems and wastewater biofilms (Douterelo et al, 2016;Navarro et al, 2016;Shaw et al, 2014) and their abundance can increase with the chlorine concentration (Wang et al, 2019b). The Comamonadaceae family was commonly found in water and chlorinated biofilms (Wang et al, 2019a;Zhang et al, 2019).…”

Surface Modification by Nano-Structures Reduces Viable Bacterial Biofilm in Aerobic and Anaerobic Environments

“…Microbial adhesion and the subsequent formation of a biofilm on surfaces in a liquid environment is a natural phenomenon. However, these infections are difficult to detect [ 1 , 2 ], comprising a significant concern in different fields ranging from medical devices, surgical equipment, biosensors, water distribution systems [ 3 , 4 ], food storage [ 5 , 6 ] and industrial and marine instruments [ 7 , 8 ]. The commonly applied strategies to combat biofilm formation involve the prevention of initial bacterial adhesion to surfaces and biofilm degradation.…”